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<h2><span class="refentrytitle">Function has_env_var</span></h2>
<p>boost::proto::has_env_var — 
          For testing to see whether a value exists in a transform environment corresponding to the
          specified <code class="computeroutput">Key</code>.
        </p>
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<h2 class="refsynopsisdiv-title">Synopsis</h2>
<div class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../proto/reference.html#header.boost.proto.transform.env_hpp" title="Header &lt;boost/proto/transform/env.hpp&gt;">boost/proto/transform/env.hpp</a>&gt;

</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Key<span class="special">,</span> <span class="keyword">typename</span> Env<span class="special">&gt;</span> 
  <span class="keyword">typename</span> <a class="link" href="result_of/has_env_var.html" title="Struct template has_env_var">proto::result_of::has_env_var</a><span class="special">&lt;</span><span class="identifier">Env</span> <span class="special">&amp;</span><span class="special">,</span> <span class="identifier">Key</span><span class="special">&gt;</span><span class="special">::</span><span class="identifier">type</span> 
  <span class="identifier">has_env_var</span><span class="special">(</span><span class="identifier">Env</span> <span class="special">&amp;</span> e<span class="special">)</span><span class="special">;</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Key<span class="special">,</span> <span class="keyword">typename</span> Env<span class="special">&gt;</span> 
  <span class="keyword">typename</span> <a class="link" href="result_of/has_env_var.html" title="Struct template has_env_var">proto::result_of::has_env_var</a><span class="special">&lt;</span><span class="identifier">Env</span> <span class="keyword">const</span> <span class="special">&amp;</span><span class="special">,</span> <span class="identifier">Key</span><span class="special">&gt;</span><span class="special">::</span><span class="identifier">type</span> 
  <span class="identifier">has_env_var</span><span class="special">(</span><span class="identifier">Env</span> <span class="keyword">const</span> <span class="special">&amp;</span> e<span class="special">)</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="id-1.3.32.5.46.17.4"></a><h2>Description</h2>
<p>
            See also:
            </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><code class="computeroutput"><a class="link" href="functional/has_env_var.html#id-1_3_32_5_44_1_1_7_2_5_1-bb">proto::functional::has_env_var::operator()</a></code></li></ul></div>
<p>
          </p>
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<td><p><span class="term">Returns:</span></p></td>
<td><code class="computeroutput"><a class="link" href="functional/has_env_var.html" title="Struct template has_env_var">proto::functional::has_env_var&lt;Key&gt;</a>()(e)</code></td>
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<div class="copyright-footer">Copyright © 2008 Eric Niebler<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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